There are many particle separators using airflow. Many of them are apparatuses for separating particles with a horizontal airflow into those to be flown away by air and those to fall down by an inertial force. Representative vertical separators are zigzag classifiers. Zigzag classifiers are apparatuses that separate particles into those to float upward in a zigzag column by being carried by airflow, and those to fall down. Zigzag classifiers hardly produce intermediate products and can realize fast separation, but have a slightly poor separation precision. Meanwhile, from the era of the former Agency of Industrial Science and Technology, the present applicant has consecutively explored techniques using a straight column and a straight column having a pinch (an orifice), and have filed many patent applications for such techniques (see PTLs 1 to 5).
PTL 1 relates to an airflow separation method and apparatus for solid matters, using a structure in which the first stage is not a column but is simply a fluid bed above a net, through which acicular matters are let to fall below the net, and the second stage is a column through which lump matters are separated into heavy products and light products.
PTL 2 relates to an airflow separation method and apparatus for solid matters, using two columns. First, the matters are fed into a first column for separating light products and intermediate products. Light products are discharged and recovered from the top of the first column, and intermediate products are let to fall down and slide over a net to be fed into a second column. Through the second column, they are separated into intermediate products and heavy products. In this patented technique, two blowers are used to send air individually to the two columns having a fixed cross-sectional area, the order to recover the products is light products first and intermediate products/heavy products next, and the products are let to move from the column to the column by gravitational fall above a net.
PTL 3 relates to a multi-stage wind-force separator that realizes multi-stages in one column by changing the diameter of the column stepwise with a diffuser. Because a plurality of columns are arranged coaxially, airflow is generated with one blower basically. However, because a wind speed ratio is generated between two columns with introduction of a second airflow, a plurality of blowers are necessary after all.
There are many common cyclone separators. They utilize a centrifugal force generated by a rotational flow, and convey minute particles together with air by carrying them on the rotational flow and separate them from heavy particles departed from the rotational flow. A wind-force separator of PTL 4 relates to an example in which a straight column airflow separator is combined with a cyclone in order to discharge intermediate products.
Further, PTL 5 presents an example of an airflow separator for solid matters, which is for the purposes of merely separating into three classes without asking a high precision, using an airflow separator with a straight column or an orifice-provided straight column.